The semiconductor integrated circuit (IC) industry has experienced rapid growth. Over the course of the growth, functional density of the semiconductor devices has increased with the decrease of device feature size or geometry. The scaling down process generally provides benefits by increasing production efficiency, reducing costs, and/or improving device performance, but the other hand increases complexity of the IC manufacturing processes.
To address the increase of manufacturing complexity, similar advances in IC processing and manufacturing are necessary. For example, in pursuit of higher device density, the continuing decrease in technology nodes has lead to a desire to replace a typical polysilicon gate electrode with a metal gate electrode to improve device performance. Also, a three dimensional transistor, such as a fin-like field-effect transistor (Fin-FET), has been introduced to replace a planar transistor. In the manufacturing process of the Fin-FET devices, further improvements are constantly necessary to satisfy the performance requirement in the scaling down process.